The present invention relates to continuous production of acrylamidoalkanesulfonic acid in a small reactor in connection with acrylic fiber production.
Acrylamidoalkanesulfonic acids are commercially important monomers, useful in the preparation of copolymers suitable for number of applications, including ion exchange resins, polymers useful for increasing the affinity of acrylonitrile copolymers for basic dyes, copolymers useful as resins and films, as well as in the preparation of flocculants, dispersants, adhesives, and thickeners. (The term xe2x80x9ccopolymerxe2x80x9d as used herein includes terpolymers and other higher order copolymers.)
The preparation of such monomers is known. Manufacturing processes generally involve extensive isolation, purification, and recycling steps. U.S. Pat. No. 3,544,597, Killam, Dec. 1, 1970, discloses a process of preparing lower alkyl- and olefinic-amido-sulfonic acids. A nitrile, olefin and fuming sulfuric acid are sequentially mixed together at a temperature of betweenxe2x88x9230xc2x0 and 45xc2x0 C. The resulting sulfonated amides are insoluble in an excess of the nitrile employed as the sole solvent, the amides being obtained directly by filtration and in a high state of purity.
Acrylamidoalkane sulfonic acids can be used as dye sites in acrylic fibers. There are several processes for the polymerization of acrylonitrile or other acrylics for acrylic fiber production. U.S. Pat. No. 4,255,532, Daftary, Mar. 10, 1981, discloses an acrylic polymer composition for melt spinning. A combination of a major amount of acrylonitrile and a minor amount of another monomer copolymerizable with acrylonitrile when grafted onto polyvinyl alcohol provides an improved acrylonitrile polymer for preparing fiber by extruding a fusion melt of such polymer and water.
U.S. Pat. No. 2,893,712, Wilkinson, May 9, 1961, discloses polymers of acrylonitrile containing polymerizable sulfonated vinyl monomers. The monomers may be represented by the formula CH2xe2x95x90C(R)CONHRxe2x80x2(SO3X)n. Polymerization of the monomers and copolymerization of these monomers with hydrophobic monomer such as acrylonitrile may be carried out using the crude aqueous reaction product or by using the purified materials. In an example, sodium 2-methacrylamidoethanesulfonate is prepared and the crude product filtered and dried. The crude product is copolymerized with acrylonitrile by a continuous procedure.
The present invention solves the problem of extensive purification and recycling of reactants in the manufacturing of amidoalkanesulfonic acids by integrating the process for the manufacture thereof with the manufacture of acrylic fibers.
The present invention provides a method for preparing and/or supplying an amidoalkanesulfonic acid feed stream suitable for incorporation into a polymer, comprising (a) combining under reactive conditions a molar excess of an unsaturated nitrile, a source of SO3 and of the elements of water, and an olefin, in a substantially non-aqueous medium wherein the molar ratio of water to SO3 is about 0.5 to about 1.5, thereby forming an amidoalkanesulfonic acid as a component of a crude reaction product; and (b) transferring the crude reaction product from (a), without substantial purification steps, into an apparatus for incorporation of the amidoalkanesulfonic acid into a copolymer.
The invention further provides a method for preparing a copolymer comprising amidoalkanesulfonic acid monomer units and unsaturated nitrile monomer units, comprising the steps of (a) transferring into a polymerization reactor the crude reaction product prepared by the above-described method and (b) polymerizing the resulting material
Otherwise stated, the invention also provides a method for preparing a copolymer comprising amidoalkanesulfonic acid monomer units and unsaturated nitrile monomer units, comprising the steps of (a) transferring into a polymerization reactor (i) the crude reaction product prepared by the above-described and (ii) an unsaturated nitrile monomer in addition to any unsaturated nitrile monomer which may be present in (i); and (b) polymerizing the resulting mixture.